#include <iostream>
using namespace std;

class student
{
	int _a;
public:
	student(int,int);
	student();
	~student();
};
student::student()
{
	cout << "默认构造" << endl;
}
student::student(int a,int=10)
{
	_a=a;
	cout << "有参构造" <<_a << endl;
}
student::~student()
{
	cout << "析构" << _a  << endl;
}
int main()
{
	student a;
	student b(2);
	student c=student(3);
	return 0;
}
